Hark; the time hath come for "Hey, Science," our intelligence-boosting feature in which we enlist real live scientific experts to answer humanity's most interesting/ idiotic scientific questions. Today: Is there an evolutionary or biological reason for preferring to have sex with people of a certain race?

The question, from reader M.: "Is some humans' sexual preference or sexual propensity for certain other humans of a particular 'race' a biologically determined orientation or a culturally constructed desire or a combination of both?" That is, can evolutionary biology tell us the reason why you're only "into" a certain race of person, for boning? Does the answer lie deep in your DNA? Or are you just a boring racist?

Donald Symons, professor emeritus of anthropology at UCSB and author of The Evolution of Human Sexuality:

This is a much more complicated question than it seems. The best I can do is to suggest a few things to think about.

First, during the vast majority of human evolutionary history our ancestors wouldn't have traveled far from their birthplace and therefore would rarely have encountered individuals who looked very different from themselves or other members of their group—i.e., people of different "races." Thus, it's very unlikely that we evolved any psychological (brain) adaptations, sexual or otherwise, that have to do with "race." That's not to say, of course, that our ancestors didn't detect and act on in-group/out-group differences, just that these weren't "racial" differences.

Second, mate choice was an important adaptive problem facing our ancestors, so we should expect natural selection to have produced specialized psychological mechanisms designed to solve this problem. Mate choice actually comprises many different problems, so we should expect the evolution of many different mechanisms to solve them. Some problems might be solved by mechanisms that requires little input from the environment, and therefore develop in the same way in every environment. E.g., what's the ideal amount of acne or other visible skin diseases in a potential mate? Presumably zero. So a psychological mechanism that follows the "rule": "prefer unblemished skin, all else equal," would have been adaptive everywhere, and would develop in a relatively "innate" manner. But what about, say, skin color? Ancestral human populations lived in a wide variety of environments and consequently evolved very different skin colors to cope with those environments. And there was always some gene flow throughout the range humans lived in, which is why we remained a single species. So one would not expect selection to have favored an "innate" preference for any specific skin color. What would have made adaptive sense is a mechanism that detects skin color in the individuals one sees growing up and specifies a rule "prefer a mate with the average skin color you've seen." And that seems to be more or less what did evolve, with one caveat. Human female skin that is a bit lighter than the local average was a reliable cue of nubility (women's skin in the environments of evolutionary history tended to darken a bit with age and successive pregnancies). All else equal, the best mate was a nubile woman, so the most attractive female skin color in ancestral human environments probably was a bit lighter than the local female average. Although it's been some years since I read the scientific literature on this topic, the evidence I'm aware of supports this prediction.

Obviously the environments of modern industrialized societies differ in many important ways from those of our ancestral past, so there are lots of evolutionary novelties to consider, including: individual variation in physical appearance is far greater in industrialized societies than it was under ancestral conditions; in industrialized societies different people are exposed to different local samples of their population; people are exposed almost from birth to media images; and even mirrors, which provide a clear, stable image of oneself, constitute an evolutionarily-novel input into our visual system that may affect the development of the brain mechanisms that underpin our perceptions of physical attractiveness.

These ideas are developed in much greater (and probably more coherent) detail in my chapter, "Beauty is in the adaptations of the beholder," in the book Sexual Nature/Sexual Culture, edited by Paul Abramson and Steven Pinkerton, and in a little book by Catherine Salmon and me, Warrior Lovers.

Pierre Van Den Bergh, professor emeritus of sociology at the University of Washington and author of many books on race, sexuality, and human evolution:

I believe the "natural" sexual preference is for partners who are broadly similar to oneself, in good physical condition, and in control of good resources, especially for women. Men tend to be more open to any mating opportunity, and to be less choosy. Any narrow preference for a particular type of sexual object, I tend to view as a form of culturally conditioned fetishism brought about by prior experiences, whether it be blond hair, red shoes or rubber gloves.

Brendan Zietsch, research fellow at the University of Queensland School of Psychology, studying human sexuality:

The question is an interesting one. The short answer is: probably yes [it is determined by evolution] but we don't know for sure. We do know that virtually all psychological characteristics that have been studies are to some extent heritable. In fact, my own research shows that, compared with genetically nonidentical twins, genetically identical twins have more similar sexual and romantic partner preferences, which indicates that genes play a role in those preferences. No one has looked specifically for genetic influences on sexual preferences for different races, but I see no reason why this would not be to some extent heritable as well. It is important to note that 'to some extent heritable' does not mean that these preferences are 'biologically determined', only that genes play some role along with environmental influences which could include upbringing and cultural prejudices.

The verdict: Though this is far from a settled question with a definitive answer, the consensus seems to be that evolution and genetics do likely play some role in humans' sexual preferences—quite possibly including racial preferences, although the exact nature of what goes into forming such preferences is unclear.

We can say definitively that there is not enough evidence for anyone to be able to say, "I only date [race] [women, men, or both] because that's in my genes." Open your minds, people. And your legs!


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[Image by Jim Cooke]